HGM Controller w/ 4L80. Speedo too Fast!

[MJ_Bone]

Hi folks. I'm new but hopefully someone here can help me out anyway lol.

I have a 2002 Z/28 which I converted from M6 to 4L80. It's all back together and it shifts through the gears and the speedo reading on the Compushift is accurate.

Here is the problem: The problem is that the speedo in the car is reading way high. As instructed, I connected the reproduced TOSS output wire from the Compushift to the purple/white wire on the car.

Any thoughts on how to correct this? Anyone in the same boat?

Thanks for any advice you can offer!

[Steve Chryssos]

EDIT: I'm wrong. Back at shop--brain on: Use the purple/white wire. The problem with your swap is that your '80 uses a different reluctor wheel than your old six speed. Best fix is to install a speedo corrector unit for your application.

Classic Instruments SN77 or Dakota Digital SG15. It's the same part. Classic buys them off Dakota.

[MJ_Bone]

Thanks Steve. I think/hope a speedo correction box does the trick. But what bothers me is that I thought the HGM controller was supposed to do the job without correction. And as far as I know, the T56, 4L80E, and 4L60E all use 40 tooth reluctor rings.

That being said, I didn't actually count the lugs on my reluctor, I was just happy to see that there was one in there at all. (The first time I got this trani back from the shop the reluctor was missing and I didn't realize it until the car was fully assembled!)

[fishtail8]

Make sure your tooth count is right, if you have the programable box you did change the input and the number? I'm just checking things in my head, I run the Compushift and a 4L80E with no problems. If you need I can check my settings in the truck next time I'm near it.

[MJ_Bone]

Make sure your tooth count is right, if you have the programable box you did change the input and the number? I'm just checking things in my head, I run the Compushift and a 4L80E with no problems. If you need I can check my settings in the truck next time I'm near it.

Thanks fishtail8. I spoke with Mike at HGM a while back, very helpful guy, the conversation is getting a little fuzzy with time, but I believe he indicated that the programability of his controller only effects the incoming signal coming from the trani, and it does not effect the controller's reproduced TOSS (which is sent to the speedo gage.). In other words, the reproduced TOSS is not adjustable by means of the Compushift controller.

What kind of vehicle are you using Compushift on?

[fishtail8]

I've got a 4L80E behind my big block in a 83 dually. To run the factory speedo, i had to buy an extra box to run the speedo via electric motor. It uses the signal off the Compushift through a bunch of dipswitches to find the right rpm to drive the motor at. It works ok, but gets picky in the cold. In the future i'll probably put an electric speedo in the dash and wire it up.

Does it effect it any if you move the reluctor ring count around? Just for something to try? I'll get out and look at the truck in the am. It's -21C right now... i'll stay inside...

[MJ_Bone]

I'll have to correct this sooner than later. I'm bouncing off the max speed limited to 163 mph when I really only going around 65-70 mph.



....shopping for a buffer box.